The present invention relates to a control apparatus for an air brake, especially for an aircraft. Conventionally such air brakes are operated pneumatically or hydrualically by means of a respective power amplifier comprising a pressure cylinder and a piston, whereby the latter is coupled mechanically to the air brake flap in such a manner that the piston displacement is about proportional to the angle of the air brake flap.
Control means of the just described type are used in aircrafts capable of high sub-sonic speeds, as well as super-sonic speeds, whereby high dynamic or impact pressures occur. In designing the control devices for such air brakes certain given or required decelerations of the aircraft at given speeds and at certain altitudes must be taken into account, whereby certain maximum decelerations must not be exceeded. In the light of these requirements, prior art control devices have the drawback that they provide an adequate braking action at low speeds, however, at high speeds, for example, corresponding to the speed of sound or a multiple of the speed of sound such prior art control devices develop too large a braking action.
The main reason for this undesirable feature of prior art control devices is seen in the installation of the pressure cylinder, whereby due to the limited space in the retracted position of the air brake flap, only small lever arms may be employed having an unfavorable mechanical advantage. Thus, it is necessary to provide a respectively high cylinder force to achieve the required opening moment. As a result, when the air brake flap is in its opened position holding moments are employed which are excessive and which, as a result, cause undesirably high brake power. Stated differently, the holding moments are larger than those resulting from the required brake powers. This feature of prior art control devices has the disadvantages that the mechanical features of the air brake flap and the mechanical features of the surrounding cell structure in which the air brake is located, must be dimensioned for unnecessarily high brake values. As a result, the air brake arrangement becomes rather heavy. A further disadvantage of prior art devices of this type is seen in that the pilot himself must control the extent of the flap displacement of the air brake. This requirement is an additional burden to the pilot, which in an emergency or in a military aircraft may have dangerous consequences.
As mentioned above, the flaps of the air brakes may be controlled by hydraulic or pneumatic means, whereby the former may include so called hydraulic torque motors. Any of these drive or control means must be supported in the aircraft structure. Hence, the latter must be capable of taking up or providing the necessary reaction forces.